Middle ear inflammations and resulting complications represent an extremely common health and social problem. The etiology and pathogenesis of the various inflammatory middle ear diseases beginning with the middle ear effusions, such as serous otitis media and including the various forms of chronic otitis media are largely unknown. Through a study of these mechanisms, improved methods of treatment and prevention will result. Another important aspect is what appears to be a common complication of otitis media, sensorineural hearing loss. This phenomenon may be more prevalent in causing sensorineural hearing loss in children and adults than is presently realized. Our objective is to study the etio-pathogenesis of the various middle ear inflammatory diseases which can occur along a continuum and may be dynamically interrelated, as well as the pathogenesis of sensorineural hearing loss as may develop from round window diffusion of toxins. We concentrate our study on the precursor acute states (middle ear effusions including acute otitis media) leading to chronic otitis media and study the immediate, intermediate and advanced cellular changes of these inflammatory diseases. This multi-disciplinary study in both human and animal subjects is expanded to include methods applicable to the following disciplines: 1) morphology and pathology (normal base line information and induced cellular changes including histochemistry, autoradiography and electronmicroscopy); 2) biochemistry and immunochemistry (chemical alterations of the middle ear effusions and perilymph in serous labyrinthitis); 3) functional assessment (humans and animals) to investigate very high tone losses.